Ultrasonic Testing In Recognition Of Multi-pattern Weld Defects

The safe and stable operation of electric power equipment is an important prerequisite for power companies to ensure the safety and quality of electricity.As electric power equipment becomes more and more large-scale,and the scale of power grids is getting larger and larger,in the event of equipment failure,it will have a huge impact on industrial production and residents' lives.Welding structure is an unavoidable part of power equipment.In this type of structure,due to factors such as welding techniques and work environment,cracks,air holes,and other types of defects are sometimes present.During the operation of the equipment,excessive pressure,high frequency vibration,etc.,may lead to the occurrence of defect expansion,stress concentration in the weld and other dangerous conditions,resulting in the unit non-stop,key welding failure,etc.It is hard to measure the loss of company.In this paper,the ultrasonic testing technology of weld defects in power equipment is studied.Based on the ultrasonic testing technology,a weak rigid matching ultrasonic transducer is developed,and the direct contact coupling detection of the weld is realized,which helps the inspection personnel to perform the ultrasonic testing of welding structure quickly and accurately.The main contents of this thesis are as follows:(1)The propagation law of ultrasonic waves in solids is analyzed,and the sound field parameters of ultrasonic waves with different frequencies and sizes under direct coupling of multi-state complex curved surface welds are studied;(2)The ultrasonic waves in welding consumables are studied.Propagation characteristics,designed the geometry of special weak rigid ultrasonic transducers(including size,shape,etc.);(3)Obtained a variety of different types of weld defects by artificial scratching,and analyzed the time and frequency domain characteristics of different ultrasonic echo signals;(4)Designed a multi-state complex curved surface weld directly coupled ultrasonic testing system,the detection of the artificial specimen and the actual components were carried out.Through this study,the results show that: after on-site testing of multi-state complex surface welds,the developed weakly-matched ultrasonic transducers can help the inspection personnel to detect defects quickly and accurately during the actual inspection process and reduce the traditional weld seam inspection.The surface polishing time required for traditional weld inspections is reduced.The type of defect can be identified to some extent based on the ultrasonic echo signals.